Enable debug info in materials in debug builds.

This lets you see highly readable GLSL when transpiling the generated
SPIRV back to GLSL, with the original variable names preserved.

For now this is only useful when using `matinfo`, but it will soon be
useful in `matdbg` too.

CMakeLists.txt

@@ -448,8 +448,9 @@ if (FILAMENT_SUPPORTS_METAL)
     set(MATC_API_FLAGS ${MATC_API_FLAGS} -a metal)
 endif()
 
+# Disable optimizations and enable debug info (preserves names in SPIR-V)
 if (FILAMENT_DISABLE_MATOPT)
-    set(MATC_OPT_FLAGS -g)
+    set(MATC_OPT_FLAGS -gd)
 endif()
 
 set(MATC_BASE_FLAGS ${MATC_API_FLAGS} -p ${MATC_TARGET} ${MATC_OPT_FLAGS})

libs/gltfio/src/MaterialGenerator.cpp

@@ -325,6 +325,7 @@ static Material* createMaterial(Engine* engine, const MaterialKey& config, const
 
     if (!optimizeShaders) {
         builder.optimization(MaterialBuilder::Optimization::NONE);
+        builder.generateDebugInfo(true);
     }
 
     static_assert(std::tuple_size<UvMap>::value == 8, "Badly sized uvset.");